A California Supreme Court ruling Monday makes it easier for citizens to use ballot initiatives to raise taxes, potentially boosting campaigns to use public money for stadiums, convention centers, roads, housing and other projects.

Ever since Proposition 218 passed in 1996, it was interpreted that the state constitution required at least two-thirds of voters to approve local ballot measures that raise taxes for a specific projects, a high threshold intended to curtail tax increases.

But Monday’s 5-2 court ruling says the proposition doesn’t apply to such citizens’ initiatives, but instead only government efforts to raise taxes.

The ruling appears to lower the threshold needed to pass citizens’ initiatives to a simple majority, though some dispute it will have that effect. But some called it a game-changer.

“It really does do whatever metaphor you want, move the goal lines, change the playing field, lower the hoop,” said Carl Luna, a political science professor at San Diego Mesa College.

That change was applauded and condemned.

“It’s hard to overstate how important this ruling is,” said state Sen. Scott Wiener, D-San Francisco. “Communities will now have a much easier time funding schools, transportation and other critical needs.”

Jon Coupal, president of the Howard Jarvis Taxpayers Association, warned of a spate of tax increases on their way to city and county ballots.

“I don’t think there’s any way we can sugarcoat this,” Coupal said. “This is a significant decision that will lead to unbridled collusion between local governments and special interest groups.”

He said he will seek to amend the state constitution requiring the two-thirds vote for citizens’ initiatives.

Writing for the court majority, Justice Mariano-Florentino Cuéllar made clear that the constitution does not apply the same limits on government and citizens when it comes to taxation.

“Multiple provisions of the state Constitution explicitly constrain the power of local governments to raise taxes,” he wrote. “But we will not lightly apply such restrictions on local governments to voter initiatives, ‘one of the most precious rights of our democratic process.’”

But a tax is a tax, no matter its origins, Justice Leondra R. Kruger wrote in a dissent.

“A tax passed by voter initiative, no less than a tax passed by vote of the city council, is a tax of the local government, to be collected by the local government, to raise revenue for the local government,” she wrote. “None of this could have been lost on the electorate that, also by initiative, amended the California Constitution to set ground rules for voter approval of local taxes.”

The ruling won’t affect previous tax-raising initiatives that received more than 50 percent support but less than a two-thirds majority, unless the proponents had sued pending the outcome of this ruling. It would not impact other initiatives that do not raise taxes, such as SoccerCity, the measure to go before San Diego voters next year to construct a large commercial and residential development — and a soccer stadium — at the Mission Valley site of Qualcomm Stadium

The ruling, had it been in place, would not have affected high-profile ballot initiatives last November: Measure C (to raise hotel taxes to build a new Chargers stadium) and Measure D (to raise hotel taxes to pay for a downtown San Diego convention center annex while allowing educational facilities at the Qualcomm Stadium site in Mission Valley). They faced the two-thirds threshold at the time and received only 44 percent and 41 percent of the vote, respectively.

The ruling is already prompting warnings about its possible consequences.

“What will happen now is that the special interests that want to get their hands on public money for their pet projects will float voter initiatives, ” San Diego attorney Cory Briggs said. “That’s all it really benefits, the special interests.”

He was a leading author of November’s Measure D, one of the hotel tax initiatives.

The San Diego Tourism Authority said the ruling might make it easier to move forward with plans to expand the San Diego Convention Center.

For first time in 28 years, the rooftop sails at San Diego’s convention center are coming down, to replaced by an all new sails pavilion.

“The two-thirds threshold is a very high mark to reach, and it doesn’t take a lot of opposition to convince someone to not vote for something,” said Joe Terzi, the authority’s CEO. “So I would expect the industry would sit down and take a good hard look at this and move very favorably toward getting that initiative put forth.”

Mayor Kevin Faulconer has proposed a hotel tax increase to expand the center, help fix roads and fund services for the homeless. The City Council thwarted his plans to put that measure on the ballot in a special election this November, instead suggesting the plan or something like it might go before voters next year.

The mayor will now consider other options for his proposal.

“This ruling is certainly a game-changer,” the mayor’s office said in a statement Monday. “In light of this decision, we’ll be looking at what the best path forward is to get the convention center expanded and create dedicated funding streams for homelessness and road repair. In the end, the initiative’s ultimate success will be more dependent on building a broad coalition of support than what the voting threshold will be, and the Mayor is committed to getting this across the finish line.”

Citizens’ initiatives can bring needed reforms, but this ruling will make it easier to raise taxes across the state, and will likely make long ballots even longer, the San Diego Taxpayers Association said.

“Voters are going to have to be more vigilant; our system depends on their ability to stay informed and make smart choices for their communities,” the group’s CEO, Haney Hong, said.

Monday’s ruling involved a 2014 initiative in Upland in San Bernardino County to impose a $75,000 annual licensing and inspection charge on medical marijuana dispensaries.

California Cannabis Coalition vs. City of Upland went to the Supreme Court from the the Fourth District Court of Appeal, which many believe ruled that citizens’ initiatives are held to the lower vote threshold. Not everyone agrees that’s the result of Monday’s ruling.

The facts in the case are so unique that the state Supreme Court decision doesn’t address the distinction between different thresholds as it relates to tax increases proposed via initiative, said Roger Jon Diamond, a Santa Monica attorney who argued the case on behalf of Upland’s medical marijuana proponents.

“I believe that this does not affect one way or the other whether you need a two-thirds vote or simple majority,” Diamond said.

However, Justice Cuéllar, with a literary flourish, suggested that citizens’ initiatives are not bound by the government’s two-thirds restriction:

“As Ulysses once tied himself to the mast so he could resist the Siren’s tempting song … voters too can conceivably make the clear and important choice to bind themselves by making it more difficult to enact initiatives in the future,” he wrote. “The electorate made no such clear choice to tie itself to the mast here.”

Contributing to this story were staff writer Lori Weisberg and Liam Dillon, who writes for the California News Group, publisher of the Union-Tribune and Los Angeles Times.